A biometric authentication system extracts a biometric feature from a biological body input from a user and performs an identity verification by comparing the biometric feature with an enrolled biometric feature. For example, in an authentication using a fingerprint, a palm print, a vein or the like, a biometric image is generated from information obtained from a biological body part of the user by a sensor. And a biometric feature for identifying an individual such as a feature point such as an edge point or a branched point or a direction of a linear-shaped pattern is extracted. And the extracted feature is used for the authentication.
However, biometric features extracted from a user fluctuate in accordance with an inputting method or an environment. A feature point appearing in one of biometric images may not appear in the other. That is, there may be variability in the extracted biometric feature. The variability may cause increasing of an error in the identity verification. And so, there are disclosed technologies that influence of the variability is suppressed (for example, see Japanese Patent Application Publications No. 2001-344604 and No. 2010-61528).